• Journal of Photoscience
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• v.11 no.3
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• pp.89-94
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• 2004

Motile cyanobacterium Synechocystis sp. PCC 6803 cells show photomovement with respect to the light stimulus. Under lateral irradiation, Synechocystis displays a phototactic gliding movement toward the light source by a twodimensional random biased walk. Under vertical irradiation, Synechocystis decreased the frequency of mean vectorial gliding speed dependent on the applied fluence rate, whereas the deviation distribution width of the speed increased. This strongly suggests the involvement of photokinesis. Evidence for the cyanobacterial photokinesis was discussed in the previous report (Choi et al., 1999. Photochem. Photobiol. 70, 95-102) demonstrating that the gross scalar speed of vertically irradiating cells increased by about 50% compared with that of dark-adapted cells. In the visible wavelength range, Synechocystis cells showed a maximal photokinetic activity at 420 nm and a second maximal activity at 680 nm. The threshold action spectrum for the photokinesis resembles the absorption spectrum of chlorophyll with major differences in the phototaxis action spectrum at 560 nm and 660 nm. We postulate that the cyanobacterial photokinesis is powered by the energy-generating chlorophyll pigments.

• Microbiology and Biotechnology Letters
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• v.31 no.2
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• pp.103-110
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• 2003

The regulation of pyrimidine nucleotide synthesis has been proved to be controlled by a regulatory protein PyrR-mediated attenuation in the Gram-positive bacteria. After several bacterial genome sequencing projects, we have discovered the PyrR orthologues in the databases for Haemophilus influenzae and Synechocystis and sp. PCC6803 genome sequences. To investigate whether these PyrR orthologue proteins regulate pyrimidine nucleotide synthesis as well as the cases of Bacillus, the PyrR regions of each strains were amplified by PCR and cloned with pUC19 or T-vector in Escherichia coli and with a shuttle vector pHPS9 for E. coli and B. subtilis. For the regulation test of the PyrR orthologues, the aspartate-transcarbamylase (ATCase) assay was carried out. From the results of the ATCase assay, it was confirmed that Synechocystis sp. PCC6803 could not restore by pyrimidines to a B. subtilis, PyrR but H. influenzae PyrR could. For Purification of PyrR orthologue proteins, PyrR orthologue genes were cloned into the expression vector (pET14b). Over-expressed product of PyrR orthologue genes was purified and analyzed by the SDS-PACE. The purified PyrR orthologue proteins from H. influenzae and Synechocystis sp. PCC6803 turned out to be molecular mass of 18 kDa and 21 kDa, respectively. The result of uracil phosphoribosyl transferase (UPRTase) assay with purified PyrR orthologue proteins showed that H. influenzae PyrR protein only has UPRTase activity. In addition, we could predict several regulatory mechanisms that PyrR orthologue proteins regulate pyrimidine de novo synthesis in bacteria, through phylogenetic analysis for PyrR orthologue protein sequences.

• Environmental Engineering Research
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• v.20 no.4
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• pp.347-355
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• 2015

The growth kinetics of phototrophic microorganisms can be controlled by the light irradiance, the concentration of an inorganic nutrient, or both. A multi-component kinetic model is proposed and tested in novel batch experiments that allow the kinetic parameters for each factor to be estimated independently. For the cyanobacterium Synechocystis sp. PCC6803, the estimated parameters are maximum specific growth rate $({\mu}_{max})=2.8/d$, half-maximum-rate light irradiance $(K_L)=11W/m^2$, half-inhibition-rate light irradiance $(K_{L,I})=39W/m^2$, and half-maximum-rate concentration for inorganic carbon $(K_{S,Ci})=0.5mgC/L$, half-maximum-rate concentration for inorganic nitrogen $(K_{S,Ni})=1.4mgN/L$, and half-maximum-rate concentration for inorganic phosphorus $(K_{S,Pi})=0.06mgP/L$. Compared to other phototrophs having ${\mu}max$ estimates, PCC6803 is a fast-growing r-strategist relying on reaction rate. Its half-maximum-rate and half-inhibition rate values identify the ranges of light irradiance and nutrient concentrations that PCC6803 needs to achieve a high specific growth rate to be a sustainable bioenergy source. To gain the advantages of its high maximum specific growth rate, PCC6803 needs to have moderate light illumination ($7-62W/m^2$ for ${\mu}_{syn}{\geq}1/d$) and relatively high nutrient concentrations: $N_i{\geq}2.3 mgN/L$, $P_i{\geq}0.1mgP/L$, and $C_i{\geq}1.0mgC/L$.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.203-205
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• 2002

Light is an environmental signal that regulates photomovement and main energy source of photosynthesis in the cyanobacterium Synechocystis sp. PCC 6803 (Syn6803). Syn6803 is a popular model system for study of plant functional genomics. In this report, we adopted 2D gel based proteomics study to investigate proteins related with the light absorption and photo-protection in Syn6803. More than 700 proteins were detected on the SDS-gels stained with silver nitrate. Several proteins showing different expression level under various light conditions were identified with MALDI-TOF Mass spectrometry. As a comparison, we also conducted ICAT-based proteome study using WT and cphl (cyanobacterial phytochrome 1) mutant. A cphl deletion led to changes in the expression of proteins involved in translation, photosynthesis including photosystem and CO2 fixation, and cellular regulation. We are currently involved in TAP-tagging method to study protein-protein interactions in search for the molecular component involved in the light signal transduction of Syn6803 photomovement.

• Journal of Microbiology and Biotechnology
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• v.18 no.6
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• pp.1090-1094
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• 2008

In this article, we show that the orf slr1471 from Synechocystis sp. PCC 6803 codes for a functional member of the YidC/Alb3/Oxa1 protein family, and the encoded protein has a transmembrane topology with a common core structure. Using specific antibodies raised against the Synechocystis YidC homologous protein, we further show that the Synechocystis YidC protein appears to be predominantly localized in the cyanobacterial cytoplasmic membrane. The impact of the described findings for synthesis of membrane proteins and for protein sorting within cyanobacterial cells is discussed.

• Plant Biotechnology Reports
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• v.4 no.3
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• pp.193-199
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• 2010

An olive-green mutant was generated in Synechocystis sp. strain PCC 6803 by inactivation of the sll0396 gene. Whole-cell absorption spectra of the mutant revealed the missing of phycocyanin peak. An investigation of the low-temperature fluorescence emission spectra revealed that the $sll0396{\Omega}$ mutant has a reduced amount of phycocyanin. Western blot analysis showed that the mutant contained less phycocyanin ${\beta}$- and ${\alpha}$-subunits and lacked the 30- and 32-kDa linker polypeptides, and northern blot analysis revealed that the transcription of the 1.4-kb cpcBA gene encoding the phycocyanin ${\beta}$- and ${\alpha}$-subunits was lower in the mutant. The Sll0396 protein has a DNA-binding motif and shares homology with known response regulators. Our results indicate that Sll0396 plays a regulatory role in the transcription of the phycocyanin genes during phycobilisome synthesis.

• Korean Journal of Microbiology
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• v.41 no.1
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• pp.67-73
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• 2005

Photoautotrophic bacteria are promising candidates for the production of poly(3-hydroxybutyrate) (PHB) since they can address the critical problem of substrate costs. In this study, we isolated 25 Tn5-inserted mutants of the Synechocystis sp. PCC 6803 which showed enhanced PHB accumulation compared to the wild-type strain. After 5-days cultivation under nitrogen-limited mixotrophic conditions, the intracellular levels of PHB content in these mutants reached up to $10-30\%$ of dry cell weight (DCW) comparable to $4\%$ of DCW in the wild-type strain. Using the method of inverse PCR, the affected genes of the mutants were mapped on the completely known genome sequence of Synechocystis sp. PCC 6803. As a result, the increased PHB accumulation in 5 mutants were found to be resulted from defects of genes coding for NADH-ubiquinone oxidoreductase, O-succinylbenzoic-CoA ligase, photosystem II PsbT protein or histidine kinase, which are involved in photosystem in thylakoid inner membrane of the cell. The values of $NAD(P)H/NAD(P)^+$ ratio in the cells of these mutants were much higher than that of the wild-type strain as measured by using pulse-amplitude modulated fluorometer, suggesting that PHB synthesis could be enhanced by increasing the level of cellular NAD(P)H which is a limiting substrate for NADPH-dependent acetoacetyl-CoA reductase. From these results, it is likely that NAD(P)H would be a limiting factor for PHB synthesis in Synechocystis sp. PCC 6803.

• Journal of Plant Biology
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• v.38 no.1
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• pp.87-93
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• 1995

For understanding physiological nature of phototaxis in Synechocystis sp. PCC 6803 PTX(S. 6803 PTX), we examined the effects of some metabolic inhibitors and cation ionophore on the phototactic movement. In the presence of DCMU, which blocks the photosynthetic electron transport just after photosystem II acceptor, there was no inhibitory effect on the phototaxis up to $100\;\mu\textrm{M}$. Instead, the respiratory electron chain inhibitor such as sodium azide dramatically impaired the phototaxis in S. 6803 PTX. These observations indicate that the phototaxis is linked not to photo-phosphorylation, but to respiratory phosphorylation. When the cells were treated with un couplers such as CCCP or DNP, which dissipate the electrochemical gradient of proton($\Delta\mu_{H}+$) across the cytoplasmic membrane, these chemicals did not affect phototaxis. In contrast, when cells were treated with DCCD or NBD which deprive cells of A TP but leave $\Delta\mu_{H}+$ intact across the membrane, the phototactic movement was severly reduced. These results imply that ATP production, not proton motive force, is involved in the phototactic movement in this organism as a driving motive force. The application of specific calcium ionophore A23187 strongly impaired positive phototaxis. Calcium fluxes should be engaged in the sensory trans-duction of phototactic orientation. Finally, when ethionine was supplimented to culture media, the photomovement of this organism was inhibited. This implies that methylation/demethylation mechanism controls the process of phototaxis in S. 6803 PTX like chemotaxis in E. coli and Salmonella typhimurium.murium.

• Journal of Microbiology and Biotechnology
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• v.19 no.5
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• pp.447-454
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• 2009

The transport of spermidine into a cyanobacterium, Synechocystis sp. pec 6803, was characterized by measuring the uptake of $^{14}C$-spermidine. Spermidine transport was shown to be saturable with an apparent affinity constant ($K_m$) value of $67{\mu}M$ and a maximal velocity ($V_{max}$) value of 0.45 nmol/min/mg protein. Spermidine uptake was pH-dependent with the pH optimum being 8.0. The competition experiment showed strong inhibition of spermidine uptake by putrescine and spermine, whereas amino acids were hardly inhibitory. The inhibition kinetics of spermidine transport by putrescine and spermine was found to be noncompetitive with $K_i$ values of 292 and $432{\mu}M$, respectively. The inhibition of spermidine transport by various metabolic inhibitors and ionophores suggests that spermidine uptake is energy-dependent. The diminution of cell growth was observed in cells grown at a high concentration of NaCl. Addition of a low concentration of spermidine at 0.5 mM relieved growth inhibition by salt stress. Upshift of the external osmolality generated by either NaCl or sorbitol caused an increased spermidine transport with about 30-40% increase at 10 mosmol/kg upshift.

• Proceedings of the Zoological Society Korea Conference
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• 1998.10b
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• pp.304.2-304
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• 1998